1. Field Of The Invention
This invention relates generally to electrochemical cells and, more particularly, this invention relates to terminal means for reactive metal electrochemical cells.
2. Description Of The Prior Art
Electrochemical cells utilizing consumable, reactive metal anodes are well known. Multi-cell assemblies of such electrochemical cells or batteries to which this invention relates normally include a plurality of anodes and cathodes arranged in spaced relation within an overall case. The anodes and cathodes are provided on opposite sides of bipolar plates to define bipolar electrodes connected in series between a pair of spaced end plates which define the ends of the case. An electrolyte is flowed across the spaced faces of adjacent anodes and cathodes. Typically, the anode comprises an alkali metal, such as lithium, in elemental, compound, complex, alloy or mixture form, or alkaline earth metal in conjunction with a cathode typically of a suitable oxidized metal such as iron oxide or silver oxide, and an aqueous or non-aqueous electrolyte. The electrolyte normally comprises an aqueous solution of basic metal hydroxide.
Such cells are described in detail in numerous patents and publications, including U.S. Pat. Nos. 3,791,871 (Rowley); 3,976,509 (Tsai et al); 4,007,057 (Littauer et al); and 4,188,462 (Klootwyk), the details of the respective disclosures being incorporated herein by reference.
Terminal cells are provided on the opposite end plates of the multi-cell assembly, including a cathode terminal and an anode terminal for securing ends of conductors in electrically conducting relation to provide terminal voltage for operation of ancillary equipment. Heretofore, the terminal means conventionally comprise post-like elements which may or may not include threaded nuts, clamps or the like for connecting the ends of conductors to the terminal posts. The terminal posts conventionally are located at the centers of the end plates of the assembly. With the central location of the terminal posts, a current flow pattern through the stacked array of bipolar electrodes will, in a broad sense, be elliptical, with the current flow pattern at the ends of the ellipse being tapered toward the centrally located terminal posts. As a result, there is a non-uniform current distribution across the area of any given bipolar electrode and, consequently, the active metal consumption over the area of the bipolar electrode is not uniform. Specifically, the outer peripheral edges of the bipolar electrodes closer to the end plates of the cells have considerably less active metal consumption than the center areas of those bipolar electrodes. Obviously, this inefficiency has been tolerated for many years.
This invention is directed to solving the problem of non-uniform current distribution throughout a multiple electrochemical cell assembly, along with the non-uniform active metal consumption, by providing novel terminal means at the ends of the assembly.